1. Field of the Invention
The present invention relates to a cutting apparatus, and in particular, but not exclusively, to cutting apparatus for cutting sheet material.
2. Description of the Prior Art
When framing pictures and photographs it is usual for a piece of sheet material or cut card, known as a mountboard, to be inserted between the picture or photograph and a glass cover plate. The mountboard is provided with an aperture through which the picture or photograph can be viewed. The aperture may be e.g., square, rectangular, circular, oval or arch-shaped, and is usually provided with a bevelled edge to enhance the aesthetic appeal of the mountboard.
If a bevelled edge is desired this is achieved simply by mounting the blade of a cutter at the desired angle of bevelling relative to the planar surface of a mountboard to be cut. The angle of bevelling is normally about 45.degree. if the mountboard is cut from the front, but it can be about 135.degree. if it is cut from the rear of the card.
Square and rectangular holes in mountboards can be achieved fairly simply and quickly by a skilled operator simply by sliding a cutter along a straight edge and repeating the process until the desired shape has been achieved. This process can be used for all polygonal shapes.
Circular and elliptical shapes can be cut by using appropriate templates. However, cut mountboards produced by such methods tend to take a long time to produce, and to be of poor quality so that sanding down of the mountboard is generally necessary in order to achieve an acceptable finish.
In order to overcome these problems machines have been devised wherein an integrally mounted blade is rotated relative to a piece of board to be cut to produce a desired shape of mountboard. Circles can be cut by machines in which the blade is rotatably mounted about a central pivot. Ellipses can be cut by more complex machines in which a combination of rotational and translational movement is used to produce a desired ellipse.
There has, however, been a long-standing problem in cutting acceptable arch mountboards, more particularly, in producing mountboards which define holes known as cathedral arches. The term "cathedral arch" is used herein to refer to an arch which has an arcuate, for example, a substantially semicircular, top, substantially parallel sides which extend from the top and a base which is substantially perpendicular to each of the substantially parallel sides. The term "the arch of a cathedral arch" is used herein to refer to the top and the sides of the cathedral arch, as defined above, but not the base.
Cathedral arches are extremely difficult to cut accurately using a template and therefore recourse has been made to machine cutting techniques. More particularly, it is known to cut cathedral arches by a process in which a circle is first cut out of a piece of card and then, starting from two diametrically opposed points on the circle, two parallel longitudinal cuts are made in the card. The cuts are each of substantially the same length and so the cathedral arch can be completed by using a straight-edge guide to join the ends of the two longitudinal cuts.
This method is however time consuming to perform since it requires several independent operations to be performed. Furthermore, it requires a skilled operator in order to ensure that the finished product is acceptable, since small deviations from an ideal cutting line can result in a large reduction in the quantity of finish and therefore in the commercial value of the product. It is also difficult to keep the cutter at a constant depth of contact with the mountboard. Even if the method is performed by a skilled operator it is often the case that unsightly protrusions or indentations are visible in the region where the longitudinal cuts join the circumference of the pre-cut circle. Sanding down of these regions with a fine emery paper is thus usually required to produce a smooth finish, further adding to the cost and the time required to produce an acceptable product.
The above-mentioned disadvantages are further apparent when, as is normally the case, it is desired to cut a cathedral arch with a bevelled edge in order to produce an attractive finish to a mountboard. The bevelled edge is often a white or a light colour for contrast with a dark surface of the mounting board. This edge is thus highlighted so that any imperfections, even if small, can usually be easily seen. Since mountboards are used for displaying photographs and pictures in an attractive setting it is important that the finished mountboard should have as few imperfections as possible.
In view of the above-mentioned difficulties in cutting good quality cathedral arches, mountboards having such arches attract a price premium over those with circular or elliptical holes.
It is an object o the present invention to provide a cutting apparatus which overcomes or alleviates the abovementioned problems.
It is a further object of the present invention to provide a cutting apparatus which enable the arch of a cathedral arch in a mountboard to be cut without having to remove a cutting member from cutting engagement with the mountboard.
In accordance with a first aspect of the present invention, there is provided a card-cutting apparatus for cutting sheet material, comprising a pivotally mounted turntable upon which, in use, the sheet material to be cut is mounted, a cutter guide mounted above the turntable, a cutter movable along the cutter guide, and at least one rest which is engageable with the turntable to limit the rotation of the turntable.
The term "above the turntable" when used herein means "above the level of the turntable" and is not limited to positions directly above the turntable.
By using the above apparatus, the arch of a cathedral arch may be formed in a card by cutting a first straight edge in the card using a cutter guided by the cutter guide, rotating the turntable through 180.degree. while keeping the cutter in cutting contact with the card and cutting a second straight edge without removing the cutter from the card.
Preferably, the cutter guide comprises a substantially straight edge and preferably the turntable is rotatable through at least 180.degree., to enable conventional cathedral arches to be formed.
In use the substantially straight edge should be positioned so that a normal to the substantially straight edge passes through a pivot about which the turntable is pivotally mounted.
The apparatus may comprise one or more stoppers which are engageable with the turntable to limit the pivoting of the turntable to one or more (e.g. two or three) stoppers may also be provided, mounted along or adjacent the substantially straight edge so that when a cutter is slid along the substantially straight edge the stoppers can be used to prevent it travelling further in a particular direction. The stoppers may be slidably mounted along a member having the straight edge. Desirably the stoppers can be clamped or otherwise fixed in position relative to the substantially straight edge. There may be first, second and third stoppers along or adjacent the substantially straight edge so that when a cutter is placed contacting the first stopper, slid along the substantially straight edge until it contacts the second stopper and, after removing the second stopper from the path of the cutter, slid along the straight edge until it contacts the third stopper, the distance travelled by the cutter between the first and second and second and third stopper is substantially the same. For convenience the second stopper may be pivotally mounted e.g. by hinging so that in a stopping position it prevents the cutter from travelling along the substantially straight edge but, by pivoting the stopper about the hinge, the stopper can be removed from the path of the cutter to allow the cutter to be slid along the substantially straight edge. Desirably the second stopper is positioned to stop the cutter cutting into the mountboard at a point which has along the normal from the substantially straight edge to the pivot about which the turntable is pivotally mounted.
Desirably there are provided spaced markings at or adjacent the substantially straight edge which indicate distance along the straight edge. These markings may be closely spaced for accuracy, e.g. at millimetre intervals, and may be used for positioning the stoppers. It is not essential for stoppers to be provided for interrupting the paths of the cutter along the substantially straight edge since, for example, the markings can provide appropriate indicators for stopping the path of a cutter along the substantially straight edge.
The substantially straight edge may be an edge of an elongate member, e.g. a rule, which member may be slidably mounted on a frame so that the substantially straight edge can be moved closer to or further away from the pivot of the pivotally mounted turntable, as desired.
Means e.g. clamps or screws may be provided for releasably fixing the elongate member in position relative to the pivot when the elongate member has been positioned as desired.
The apparatus may be provided with its own cutter which may be slidably mounted to the elongate member. The blade of the cutter is desirably offset to cut a bevelled edge when in use. The angle of offsetting may be adjustable so that a desired angle of bevel can be achieved.
The turntable is preferably provided with means for supporting a mountboard during cutting of the mountboard e.g. it may be provided with a plurality of spaced pins or tacks, which are desirably removably mounted to the mountboard.
Preferably the blade of the cutter is offset to produce bevelled edge. Desirably the angle at which the blade of the cutter is offset relative to card to be cut is 30.degree. to 60.degree. or 120.degree. to 150.degree., more preferably substantially 45.degree. or substantially 135.degree.. These two alternatives are desired since a piece of card can be cut from either the front or from the back (a blade angled at 45.degree. when cutting card from the front will produce the same angle of bevel as a blade angled at 135.degree. when cutting card from the rear).
Standard cutters can be used with the apparatus of the present invention, if desired. A specially adapted cutter alternatively can be used which allows cathedral arches of narrow width to be produced.
Preferably there is provided a cutter comprising a cutter body having a substantially planar, horizontal undersurface for sliding across a mountboard to be cut, a first substantially, straight edge slidable along a cutter guide, a cutting blade pivotally mounted on a mounting plate of the cutter body and being pivotable from a non-cutting position to a cutting position in which it projects beneath the planar undersurface of the cutter body, wherein the mounting plate projects beyond said planar horizontal undersurface.
Desirably the cutter comprises a second edge opposite the first edge and a blade pivotally mounted for pivoting about a plane. Preferably this plane is at an angle of between 100.degree. and 170.degree. relative to said planar surface. Desirably when the blade is in cutting engagement with a mountboard the maximum distance between the blade and the second edge when measured along a normal to the first edge is less than 10 mm.
Preferably the plane of pivoting of the blade is at an angle of substantially 135.degree. relative to the planar surface. The distance between the blade and the second edge can be e.g. from 10 mm to 0.5 mm, more preferably from 5 mm to 1 mm.
The cutter may be generally "V" shaped in cross-section and may have a counterweight above said planar base surface to prevent the cutter toppling over due to the weight of the blade and its mounting. The counterweight may be shaped to form a handle of the cutter.
The cutter of the present invention is advantageous in that it allows the blade to cut into mountboard close to the second edge. This allows the 180.degree. pivoting of the card relative to the cutter to occur with only a small radius of pivot (as required when cutting a narrow arch) without the second edge interferring with mounting pins or other means used to hold the mountboard in position during the cutting process.
In accordance with a second aspect of the present invention there is provided a cutting apparatus comprising a pivotally mounted turntable upon which, in use, the sheet material to be cut is mounted, at least one adjustable clamp which at least partially extends over the sheet material to hold it in place during the cutting operation, a cutter guide mounted above the turntable, a cutter movable along the cutter guide and at least one rest which is engageable with the turntable to limit the rotation of the turntable.
This has the advantage that the sheet material is firmly held in place during the cutting operation and is therefore prevented from slipping during the cutting process. The provision of the clamping means has the advantage over using spikes to impale the sheet material on the turntable because it does not destroy a section of the sheet material by impaling it on spikes, thereby rendering any portions of the sheet material cut from the main section reusable. Furthermore, if a backing card is used the, sheet material and the backing card can be firmly clamped together avoiding the possibility of the sheet material moving during the cutting process.
Preferably, the at least one clamping means is a handle which is used to rotate the turntable. This has the advantage that the number of components of the cutting apparatus is reduced.
Preferably, the at least one clamping means forms an alignment means for the sheet material. This has the advantage that the clamping means doubles as an alignment means to ensure that the sheet material is correctly aligned on the turntable.
In accordance with a second aspect of the present invention, the cutter guide is pivotally mounted over the turntable. This has the advantage that the cutter guide can be lifted away from the turntable for the purpose of clamping the sheet material to the turntable, and can be rotated back to position above the turntable before commencing the cutting operation.
In accordance with a third aspect of the present invention, the cutter is attached to the cutter guide. This has the advantage that the cutter can be smoothly slid along the cutter without wobble and that a constant depth of cut is obtained.
Preferably the cutter has a spring loaded blade which cuts into the sheet material when pressure is applied to the cutter and a smoothing means which contacts the surface of the sheet material. This has the advantage that the smoothing means effectively irons out irregularities in the sheet material before it is cut by the blade. Furthermore, the smoothing means forms a steadier which helps keep the depth to which the blade contacts the sheet material constant when pressure is applied to the cutter.
In accordance with a fourth aspect of the present invention, a detent means is provided on the cutter guide to form a removable stopper for the cutter. This has the advantage that the cutter is automatically stopped by the detent means on the cutter guide so that the cutter can be kept still whilst the turntable is rotated beneath it. Furthermore, the detent means is disengaged by simply pushing on the cutter, this removes the need to remove a hand from the cutter in order to release the cutter from its stopped position, thereby allowing a more steady pressure to be maintained on the cutter.
In accordance with a fifth aspect of the present invention, the turntable has at least one detent means which holds the turntable in place when the turntable engages the at least one rest which limits the rotation of the turntable. This has the advantage that the turntable is held in place without the need to hold the handle and push the turntable into engagement with the rest.